The acquired immune[unreadable] deficiency syndrome (AIDS) is characterized by a progressive depletion[unreadable] of CD4 lymphocytes. The causative agent of AIDS, the human[unreadable] immunodeficiency virus (HIV) is a cytopathic retrovirus. Although the[unreadable] mechanisms of CD4 cell loss in HIV-infected people remains unclear,[unreadable] recent data indicate the direct cell killing of infected cells by HIV[unreadable] itself is likely responsible. An accessory gene of HIV, the vpr gene,[unreadable] plays an important role in the cytopathic effect of HIV. In the[unreadable] presence of an intact vpr gene, cultures of infected cells are nearly[unreadable] completely killed, while cultures infected with a virus that has a[unreadable] mutated vpr gene survive and replicate with the same kinetics as[unreadable] uninfected cells. Those cells that survive infection with a wild-type[unreadable] virus contain vpr genes with mutations. Furthermore, expression of Vpr[unreadable] itself alters cell cycle progression by causing cells to accumulate in[unreadable] G2/M. Vpr also plays another role in the virus life-cycle by allowing[unreadable] the pre-integration complex to enter the nucleus of infected cells[unreadable] before mitosis. This property allows HIV to infect terminally[unreadable] differentiated macrophages, an important reservoir of virus in the body.[unreadable] In this application, we seek to understand the mechanism of action of[unreadable] Vpr. Ultimately, we hope to determine if Vpr plays a role in the[unreadable] decline of CD4 cells during AIDS progression. Specifically, we will use[unreadable] a genetic screen for vpr mutations as well as site-directed mutations[unreadable] to determine the correlation between the different functions of Vpr.[unreadable] This will allow us to make models of the roles of Vpr in HIV[unreadable] pathogenesis. We will also characterize the effects of Vpr and Vpx of[unreadable] HIV-2 on cell proliferation. Next, we will characterize the cell cycle[unreadable] stage(s) affected by Vpr, and analyze the relationship between normal[unreadable] cell cycle controls and Vpr function. We will then determine the[unreadable] effects of Vpr in primary cells, and specifically determine how Vpr[unreadable] influences the half-life of lymphocytes and macrophages. Finally, we[unreadable] will use a screen for suppressors of the toxic effects of Vpr in yeast[unreadable] to Identify host cell targets of Vpr. In this application, we seek to[unreadable] understand the mechanism of action of Vpr. Ultimately, we hope to[unreadable] determine if Vpr plays a role in the decline of CD4 cells during AIDS[unreadable] progression. Specifically, we will use a genetic screen for vpr[unreadable] mutations as well as site-directed mutations to determine the[unreadable] correlation between the different functions of Vpr. This will allow us[unreadable] to make models of the roles of Vpr in HIV pathogenesis. We will also[unreadable] characterize the effects of Vpr and Vpx of HIV-2 on cell proliferation.[unreadable] Next, we will characterize the cell cycle stage(s) affected by Vpr, and[unreadable] analyze the relationship between normal cell cycle controls and Vpr[unreadable] function. We will then determine the effects of Vpr in primary cells,[unreadable] and specifically determine how Vpr influences the half-life of[unreadable] lymphocytes and macrophages. Finally, we will use a screen for[unreadable] suppressors of the toxic effects of Vpr in yeast to Identify host cell[unreadable] targets of Vpr.[unreadable]